Not too sure what you are asking, however unlocking your phone allows you to simply use any sim card to use the phone as is. Infact in Europe it is illegal to sell a locked phone. So my iPhone which is unlocked I can put any compatiable sim card in and off I go.

As for application blocks, I am unsure of what you mean? Do you mean facetime or Skype over 3G type of restrictions?

It'd be best if you could tell us what platform and what applications we're talking about so you can get an informed answer...

My Androids are unlocked and I can switch SIM cards as I please.

In the case of Android Market, there are some regional restrictions based on which SIM card you're using when you want to install new apps, but beyond that, not really.

As a silly example, I was unable to install (or even find) some free apps made by Geico (an American car insurance company) with my Canadian SIM card, but putting in my American SIM and then connecting over wifi worked perfectly. Once installed, I can still use the apps with my Canadian SIM in place.

It seems that the blocking of applications is simcard specific. We use here anything over any phone. Nothing is blocked.