Can I withdraw the BAT generated on my computer and on my mobile phone to my only Uphold account?
Yes. You can connect up to 4 browser wallets to the same Uphold account.
the 4th wallet have to be mobile browser wallet or it can be also desktop brave browser wallet.
what if I connect uphold to all 4 desktop brave browsers wallet.
This one 
Also do note, there’s no way to de-link the already connected wallet, yet.
I did but why i did not receive ads payout for 4th desktop walllet
What will happen when i uninstall the brave verified app? The data will be gone and out of 4 only 3 chance left for lifetime?
Very bad idea. If windows crush or something happens all chances gone. You never get rewards