1) The ONLY reason to ever consider 32-bit is if you have expensive hardware that doesn't have a 64-bit driver. (that applies to Windows version as well)
We have a FILM SCANNER and other scanner like that but for most people this is rare.
2) "linked like cell phones under the 64 bit"
??? Huh?
3) 4GB 32-bit:
As per the above comment, please note that is 4GB for the entire memory map (ignoring some workaround solutions). That means if you have a 2GB video card you have roughly 1.8GB left for system memory (about 0.2GB for motherboard hardware).
For non-gaming, basic usage that's probably fine for most people.
4) As said, you can only install 32-bit or 64-bit at a time from that license.
5) *I recommend upgrading to Windows 10 regardless unless there's a compatibility issue. Mostly I've only seen that with really old hardware or some dual-graphics laptops (like HD4000M + HD6000M).
**If you have 32-bit W7 installed now then you'll need a clean install to upgrade to Windows 10 64-bit. It's free for the next two days though.
If you have 64-bit W7 then simply do the W10 upgrade, and select keep files/apps.
6) W10 more info:
Aside from DX12 support for future games, there is a lot of stuff under the hood that makes W10 better. Memory management, security etc. LOTS of little things that aren't obvious right away.
W10 is also the last version of Windows according to Microsoft so it will simply continue to get upgraded whereas W8 and previous will slowly fall behind.