Is this question truly answered? You have marked it as such, so now people looking to assist others are unlikely to open the topic. Also realize that you asked it in the middle of the night in the USA where many (but not all) people who can help you are asleep. Then you also asked it at a time of year when many people are away from their computers and doing holiday activities. Be patient.
We need to know more about your particular computer model. Go to the Apple in the upper left corner > About This Mac > More, then copy and paste the main information there but omitting the serial number.
The guy getting 10.4 from another Mac actually doesn't matter. It's either a retail version disc in which case it will install on any G4, or it is a machine specific disc in which case it will refuse to do anything to your computer. Of course installing will revert the computer to the original software versions that were on hte installer disc, so you ned to update those. Most can be downloaded directly from Apple. Here's my long post on updating:
*Updating*
Certain steps appear to minimize the risk of an update producing problems.
Number one is to make sure you have a bootable clone backup of your computer in case you do need to back out of it again. This is the only guaranteed way of not having to worry about the results of an update.
Some like to boot from their installer discs or an external backup and verify (and if necessary repair) their internal drives as well as drive permissions. This is done with Disk Utility. You can verify a drive while booted from the same drive but sometimes this produces spurious errors. Repairing a drive (if necessary) has to be done while booted from another disk.
[Resolve startup issues and perform disk maintenance with Disk Utility and fsck|http://docs.info.apple.com/article.html?artnum=106214]
[Using Disk Utility in Mac OS X 10.4.3 or later|http://docs.info.apple.com/article.html?artnum=302672]
[Disk Utility's Repair Disk Permissions|http://docs.info.apple.com/article.html?artnum=25751]
You can also go to the step of booting into safe mode to do the install.
[Mac OS X: Starting up in Safe Mode|http://docs.info.apple.com/article.html?artnum=107393]
[What is Safe Boot, Safe Mode? (Mac OS X)|http://docs.info.apple.com/article.html?artnum=107392]
[Safe Boot takes longer than normal startup|http://docs.info.apple.com/article.html?artnum=107394]
I like to download the update onto my computer and install it from there rather than let Software Update do it. I know a few people who had problems with doing the update via software updater found a manual install to work.
Repair permissions again afterward.
It helps to only install one update at a time and to run the computer for a while to make sure it is behaving well.
The more cautious even like to unplug third party peripherals (see [comment by BDaqua|http://discussions.apple.com/message.jspa?messageID=9040746#9040746]).
Almost all of the above steps (except backup) have been questioned (e.g., [Permissions repair|http://www.macworld.com/article/52220-3/2006/08/repairpermissions.html]) as to necessity. Probably many people have done successful updates without doing them. I say they can't hurt, they can very likely do good (especially if your computer isn't regularly maintained), so why not do them to be safe?
[BDaqua's comments on updating problems|http://discussions.apple.com/message.jspa?messageID=8948595#8948595]
[Baby Boomer's comments on updating problems|http://discussions.apple.com/message.jspa?messageID=9025760#9025760]
[Klaus1's post on updating and removing updates|http://discussions.apple.com/message.jspa?messageID=10257902] and [another one|http://discussions.apple.com/message.jspa?messageID=10402175]
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You will have a lot of updates to do, so do them one by one, testing in between. Start with "Combo" 10.4.11 updater PowerPC-based Macs - http://www.apple.com/support/downloads/macosx10411comboupdateppc.html
Flash will be the messiest because, as you have observed, Adobe does not make it easy and it is also the most finicky.
*Flash Player for PPC Macs*
Adobe's last release of Flash Player for PPC Macs was in November, 2010 with release 10.1.102.64 Subsequent releases are for Intel based Macs only.
To check your installed version of FlashPlayer - http://www.adobe.com/software/flash/about
To update you should download:
Flash uninstaller: [http://kb2.adobe.com/cps/865/cpsid_86551.html#prob1=uninst,os=m10.6,] Make sure you get the right one.
Flash installer 10.1.102.64 [http://fpdownload.macromedia.com/get/flashplayer/installers/archive/fp_10.1.102. 64_and_9.0.289.0_archive.zip] Open the archive to reveal yet more archives and multiple files. Select: flashplayer10_1r102_64_ub_mac.dmg
To install:
1) Run Disk Utility and verify your hard drive. If the hard drive reports errors then it will need repairing first (another topic). If it verifies, run Disk Utility's repair permissions.
2) Back up your hard drive, ideally to a bootable clone. A bootable clone will allow you to restore your hard drive to its original state should something go wrong.
3) Quit all applications to ensure nothing is actively using Flash. You can even do the next step while booted to Safe Mode to make sure.
[Mac OS X: Starting up in Safe Mode|http://docs.info.apple.com/article.html?artnum=107393]
[What is Safe Boot, Safe Mode? (Mac OS X)|http://support.apple.com/kb/HT1564]
[Safe Boot takes longer than normal startup|http://docs.info.apple.com/article.html?artnum=107394]
4) Run the uninstaller application. Adobe says, "Adobe recommends that you restart your computer before you install a different version of the player."
5) Run the installer application from the .dmg file you got from the second download.
6) Use Disk Utility to repair permissions on your computer. this is important when installing anything from Adobe.
7) Restart your computer.
Notes:
Adobe installs things all over your computer. Simply dragging a file or two to the trash won't ensure you have uninstalled all old file components.
Comments about Flash and Shockwave. [http://discussions.apple.com/thread.jspa?threadID=2769507]
Flash player 11.1 hack on PowerPC - https://discussions.apple.com/thread/3558589?answerId=16990862022#16990862022
Installing last version of Adobe Flash for PPC Mac - http://discussions.apple.com/thread.jspa?threadID=2760627 Also read: [http://discussions.apple.com/message.jspa?messageID=13159407#13159407] for help with downloading for PPC Macs since Adobe no longer makes this easy.
