My current version is 3.62. Do I need to update to ver 4.0x? When I check the update, it said 3.62 is updated version
Nope, 3.62 is what I use an it’s great. Sure, there are new things in 4.0x, but I completely trust 3.62 and it does everything I need it to do.
Yeah, I think this is because ROBOTC 3.x is treated as it’s own application, as is ROBOTC 4.x. They are treated by your computer as completely different programs (for the sake of this), and if I recall correctly, you can have both installed on your computer if you wanted to simultaneously, as 4.x isn’t treated as an updated version of 3.x. Obviously you could only use your existing licence on one (I think).
As for using them with VEXnet 2.0, I am not sure about that (I haven’t been paying too much attention to VEXnet 2.0 to be honest, as we have enough 1.0 keys to last us a while). But I’m sure someone else will help out there.
Hope that helps 
EDIT: You may find this thread useful: ROBOTC V4.XX evaluation - Technical Discussion - VEX Forum
~George
Thank you very much George for your explanation and link.
No problem, glad I could help!
~George
Just to add to what George said. V4.xx is not a free upgrade to ROBOTC as it now supports the VEX IQ system as well as the cortex, support for the PIC was also dropped.
I plan to stay with 3.62 for at least the rest of this competition season, I have never managed to finish the evaluation I started in the thread that George linked and probably won’t be able to until May.
Thanks, Guys. I will keep 3.62 according to your advice.
We’re continuing to support both the 3.X and 4.X codebases for the time being. Once the VEXnet 2.0 firmware is stable with download/debug support, we’ll be releasing a 3.63 version that will include the new 4.0x master firmware. We don’t want to force users to upgrade to 4.X just to use their new VEXnet 2.0 keys
Oof, that’s a lot of version numbers in one post.
You meant if we want to use VEXnet 2.0 key, we have to upgrade ROBOTC 3.62 to 4.x.
If I understand correctly, you use RobotC 3.63 (still under development), with 4.0 firmware, so you don’t have to upgrade to RobotC 4.x.
I am using v3.62 now
Rather, you CAN use 3.63…
Sorry for the confusion.
Versions available today:
ROBOTC 3.62 (ships with old 3.x master firmware)
ROBOTC 4.06 (ships with old 3.x master firmware)
If you’re using VEXNet 2.0 keys, you’ll need to manually update your master firmware, but you can continue to use ROBOTC 3.62/4.06. For instructions on how to use VEXnet 2.0 keys with these versions of ROBOTC, take a look at our Wiki Page on Manually Updating Firmware
Once VEX gets a VEXNet 2.0 firmware version that supports wireless debug/download, we’ll update ROBOTC to 3.63/4.07 (or whatever version number is next) which will then contain the new 4.xx master firmware. We don’t know when this will be.