No, it's not. At least once you're good enough to beat the stage without that life in advance. See, Gengetu's third phase is extremely easy and exists for once reason only: To be a grazewhore's dream. It's very easy to get 10 million points just from grazing the attack, meaning that unless you did REALLY badly on the stage, you're guaranteed to reach 30 million and get the last extend. The enemies at the beginning drop power items, which you need to be able to kill the wall spamming enemies before they completely flood the screen with BS, so naturally with all this killing the enemies and getting the same points from Gengetu's third phase is the best option.
And as far as I know, the position of the explosions at the end are random (don't quote me on this though). However, because they're aimed, as long as you don't panic it's not that hard to dodge even if one's right next to you.