Q: What Happens when I restore my El Capitan mac to factory settings?

I currently have El Capitan and wanted to reinstall my Windows partition since I needed more space but after deleting the partition and setting up the new partitions, I ran into some trouble while installing windows wherein it said the drive was of GPT partition or something like that. I've wasted 3 days trying out different solutions from various sites including this and have yet to make it work so I decided to just restore my Mac to its original OS and reinstall my Windows then just upgrade to El Capitan again.

My questions are:

1. This would be the first time I'm doing this but based on what I've read and watched, are these the exact steps in restoring my mac to its factory settings?

     a. Reboot Mac

     b. Hold cmd + r

     c. Select Disk Utility under the OS X Utilities Window

     d. Select the partition (Macintosh HD)

     e. Erase it to OS X (journaled)

     f. Close Disk Utility

     g. Click Reinstall OS X under the OS X Utilities Window

     h. Click continue

     i. Select my drive

     j. Click install

2. What would be the OS X installed on my newly formatted partition? Would it still be El Capitan (My current os before formatting) or Mountain Lion (The original os on my Air mid 2013)?