[Attention Surplus Disorder]

How do they (remotely) pull the pins? Or do these rounds go off on simple impact?

[BenLurkin]

AZOV did not want their hostages to leave Mariupol
https://www.youtube.com/watch?v=31eM-USfdzE

[chaosagent]

The grenade contains a drogue parachute (visible at right inside this museum cutout), that springs out when thrown to ensure the grenade hits the target fuze-first.

On impact, the RKG-3 detonates a shaped charge (demonstrated in yellow in this cutout) that fires a hypersonic slug of copper with enough force to penetrate more than 20 centimeters of armor.

The burst of superheated metal into the interior of tanks can sometimes lead to "catastrophic" explosions of the ammunition inside.

Sounds like pulling the pin just arms it and the impact does the rest.

[Bruce Campbells Chin]

Both, actually. The pin must be pulled, but there must also be an impact. So either they pull the pins before sending them aloft (most likely), or rigged up something to pull the pins remotely. But I’d bet on the former.

[Rio]

From Wikipedia:
RKG stands for Ruchnaya Kumulyativnaya Granata (”handheld shaped-charge grenade”). The grenade has an odd strap-like lever (or “spoon”) that covers the base of the handle and runs up each side of the handle. When the pin is pulled, the “spoon” falls away, and when the grenade is thrown a spring deploys a four-panelled drogue parachute. This parachute stabilizes the grenade in flight and ensures that the grenade strikes the target at a 90 degree angle, maximising the effect of the shaped charge. Realistic accurate throw ranges are within 15 to 25 metres (49 to 82 ft). The lethality radius is within two metres (6.6 ft) due to concussion and fragmentation. The casualty radius is within 20 metres (66 ft) and the danger space from fragmentation is within 50 metres (160 ft) meters.

The fuze in the handle activates the grenade. When the parachute deploys, its ejection throws a weight to the rear of the handle and disables the safety. When it impacts or stops, inertia causes the weight to fly forward and hit the spring-loaded firing pin, which activates the primer detonator in the base. This sets off the booster charge in the base of the shaped charge, detonating and enhancing the main charge. The sensitive fuze guarantees that the grenade will detonate if it impacts any target.

Armour penetration depends on the model. The original RKG-3 used a basic shaped charge with a steel liner and could penetrate 125 millimetres (4.9 in) against Rolled Homogeneous Armor (RHA). The RKG-3M used a copper-lined shaped-charge warhead and had a penetration of 165 mm; the RKG-3T had an improved copper liner that had a penetration of 170 mm. The RKG-3EM has a larger warhead and boasts a penetration of 220 millimetres (8.7 in).