Good question; and the answers are No and No.
This is because of the soldier's non-suicidal intentionality. In this case, though death from the exploding grenade is foreseen, it is not intended (by the heroic soldier.)
In other words, if it were possible to shield his comrades by some other means (e.g. somehow dropping a 500-lb weight on the grenade) he would have done it; and if he threw himself on the grenade and it was a dud and did not go off, he would not try to find some other means of killing himself; and if it did go off and he were not killed but, say, had his legs mangled, he would still appreciate being medivac'ed out rapidly and put in the care of a skilled emergency medical- team to save his life.
This is what we call a case of "double effect," usually illustrated by a large letter
where the vertical part of the Y represents the action, and the two branching parts represent 2 effects, in this case (1)saving the lives of his comrades, and (2) dying. If only one of these effects is actually intended, and the other, though foreseen, is not intended and would be avoided if at all possible, then the soldier's action is not suicide.
Thank you, Mrs. D.
Your reasoning is much appreciated.
You must be an excellent mom.