Upgrading from iPhone 5 to iPhone 6 Plus after Water Damage

My iPhone 5 fell in water back in October of 2014. I placed the phone in a bag of rice for 3 days

straight when it happened. It dried out fine and worked like nothing happened. Didn't matter I had

to upgrade to the iPhone 6 Plus anyways since it was released around that time. I decided to leave

my last existing backup on my computer (that I did before the phone dropped in water), and not backup

the phone after the water drop. Because the data could potentially be corrupt due to the oxidization of

components inside. Long story short I have the iPhone 6 plus now I got yesterday.

What I need to know:

My iPhone 5 still works but obviously it now doesn't have a working sim card. There are apps I wanted to

take snapshots of, or files I wanted to export from various places from after the water drop happened (which

I never backed up for reasons mentioned above. I already did a backup restore to the new iPhone 6 Plus from

the backup file made prior to the water drop. The iPhone 6 Plus is working flawlessly.

Can I use both phones at the same time with the apps going at the same time? Or will their be a weird

lockout conflict of sorts? Remember one phone has a working sim, but the apps will be the same as the

old phone and I don't want to use both at the same time if it will cause problems.