Can a stinger missile shoot vehicles and infantry?

Answer 1

The Stinger missile locks onto a heat source for it's targeting... whether this sensor is capable of locking onto human body heat, I cannot say. However, it would be a very poor choice for use against armoured vehicles, as the warhead is designed to detonate near the target and use fragmentation to damage or destroy the target (since aircraft are rather thin-skinned), whereas an anti-tank warhead is designed to penetrate thick armour usually either through shaped charges or by injecting a stream of molten liquid metal into the armour, so that it pierces through and enters the crew compartment.

Even if it were capable of being used against infantry, it would not be a feasible anti-personnel weapon, whatsoever. Most firefights occur at ranges of less than 150 metres, whereas the Stinger needs 180 metres before it'll arm the warhead, and it takes several seconds to lock on and engage a target, which means that the operator would be exposed during this time.

Stingers are categorically unusable as an anti-infantry or anti-structure weapon. There is a modest possibility of getting the seeker warhead to lock onto a super-hot vehicle exhaust (such as the exhaust from certain turbine-powered tanks), but typical diesel or gas engines aren't even close to being hot enough. That said, the engagement of a ground target is completely outside the guidance system's design, and it is highly unlikely that it would work against anything other than something like a taxi-ing aircraft or a helo prep-ing for takeoff.