Hmm, deactivation once armed huh? Really up to the GM and the story intensity. However, here's my take on it:
OK, I class non-aerodynamic grenades to be made with a booby-trap feature. Something like an extendable spool wire you can use to rig tripwires or attach to the bottom of mattresses/doorhandles etc. Often accompanied with a magnetic or adhesive ability allowing them to be placed in convienient booby-trap locations. These I'd allow a character an attempt to disarm if discovered. Demolitions (Bomb Disposal) skill would be used for the test. As for the difficulty, that would depend on how it was prepared by the character who laid it - usually low to average if casually placed, higher if hidden or an extreme example. Alternatively use the Demolitions Skill Rating of the boby-trapper as the TN + 1 per success they achieved in setting the grenade. They'd also better have some tools for the job otherwise its increased TNs.
As for thrown grenades, especially the aerodynamic ones which I view as not having enough space for a booby-trap feature, they would be limited to the variable timer option as standard. The character has to set the timer with a simple action before throwing (2 seconds to 2-3 minutes, or whatever limit your GM inposes). This makes disarming them a risky venture, although it could be possible - especially for those with boosted reflexes. The timer might be electronic, but I'd still use Demolitions (Bomb Disposal) to achieve it though - after all, it is an explosive device.
Conversely, because of the advances in technology, most grenade manufacturers would have installed anti-tamper stuff by 2050s. So, good quality products would be nearly impossible to disarm. There may still be the odd low quality version still knocking about though, especially in the hands of those people not rich enough to afford the latest tech. IE: Gangers, revolutionaries, third world tribes/groups using left-over surplus munitions, etc.
As a note, I allow many grenades in my games to be equipped with a detonate upon impact function. This is a favoured option amongst my players because it happens there and then in the combat round (like airburst-programmed mini-grenades) rather than waiting until the end of the round. Which can be a little unrealistic given high initiative/action characters. Then again, they ten to be very careful in case they accidentally drop or jolt them too hard before they manage to throw them away. (Yup its fun when NPC snipers hold there actions and plug the character about to lob one, thus dropping their own weapon into the midst of the PC group - BOOM!) this can also happen on an "Oops" result of all ones on the Throwing Weapons test.

Another option is to have grenades that are equipped with sensors that trigger the explosive upon meeting the required criterea - reversal or cessation of forward inertia for example. (Technically you could lob one back if you caught it in a swinging motion and then lob it back in a clean swing.) Another option for high tech ops forces is to equip them with Personal Smartgun Safety chips, so that they won't detonate if detecting any friendly transmitter signal within their blast radius.
As for grenade launcher fired grenades - nope.