How can I exactly tell what version iMac I have?

There was no Bondi Blue at 350 Mhz. There was a blueberry 350 Mhz which looks similar and is more like the one you picked an icon for. You might do better finding your model, using my FAQ:
http://www.macmaps.com/macosxnative.html#IDENTIFY

redundant!

Here you go:

http://www.designedinca.com/macs/imac/oct1999/350/

Looks like you have an original blueberry slot loading and not a bondi blue. The avatar is an Indigo, not a Blueberry!

When I look at the link I gave you:

is alongside these specs:

iMac 350MHz (Slot Loading)

October 5, 1999 — July 19, 2000

Related events

Introduction: iMac slot-loading models debut
Retirement: Sage/Ruby/Indigo/Graphite/Snow iMac line launched
Specifications

General
Price $999 at introduction
Order No. M7469LL/A - Blueberry
Introduced October 5, 1999
Retired July 19, 2000
Computer
Processor 350MHz PowerPC G3
Frontside Bus 100MHz 60x
Cache 512KB SRAM external L2 cache at 140MHz
Memory 64MB PC100 SDRAM
Memory Slots Two DIMM slots
Hard Drive 6GB 3.5" Ultra ATA/33 hard drive
Optical Drive Compact slot-loading CD-ROM
Graphics and Sound
Graphics ATI Rage 128 VR with 8MB SDRAM on a 2x AGP bus
Monitor Ports None
TV In/Out No
Audio In/Out 3.5mm audio input
3.5mm audio output and 2 headphone sockets
Speakers Built-in stereo speakers
Connectivity
USB Two independent USB 1.1 ports
FireWire 400 None
Ethernet 10/100BASE-T ethernet port (MDI)
Modem 56K v.90 modem
AirPort No AirPort support
IrDA No
Expansion Slots No
Display
Type 15.0-inch CRT (13.8 inches visible)
Resolution 1024x768 pixels
Pixel density 93 dpi
Physical
Size (w x d x h) 15 x 17.1 x 15 inches
Weight 34.7 lb

It would seem if I copy/paste their image link directly into the board I get a different image, so I downloaded the image over to my website to make sure you get the same image I'm seeing.

Look I already told you although that avatar is blueberry my iMac is in bondi blue!

As a brody indicated, your avatar is NOT Blueberry. That avatar is Indigo.

Bondi ->

Blueberry ->

Indigo ->

...it also is a slot loader with a DVD rom drive and runs at 350 mHz.

Since none of the 350 MHz iMacs shipped with a DVD-ROM drive, someone replaced the original CD-ROM drive.

" I dont wan't to shortchange myself on perfomance."

The confirmation of your Blueberry slot-loading iMac identifies the type/maximum amount of memory to purchase: (2) 512 MB DIMMs, 168-pin PC-100 (or compatible PC-133), non-ECC, Unregistered SDRAM. Of equal significance is the 350 MHz processor, in terms of overall performance when running Tiger. Having a processor (speed) that's close to the minimum threshold requirement for running the OS, might be a reason to consider buying/installing Panther, as it's less-demanding of your iMac's hardware capabilities.

Check eBay for a retail version/universal Panther installer CD set, not a model-specific Restore CD. The retail version disks are black with a large silver X on them. Restore CDs can have problems installing on different models, in spite of a seller's claims to the contrary. I recently saw a retail Panther (10.3.5) CD set close at $36, but you might pay more. There seem to be a number of the first revision (10.3) Panther installer CD sets up for auction, which probably go for less, since they require more updating and the accompanying programs CD (Disk 2) contains older versions.