Q.Cherry Tomato Stem broke
Before I had a chance to stake my large cherry tomato plant, the main stem broke off. Is it possible to salvage it by submerging the stem in water to grow roots? Or is there some other solution? The plant has many near ripe cherry tomatoes.

You can definitely try to splice it back together if the variety you have is more of a vine than a bush, but it won't re-root. There's no guarantee that splicing or splinting it will work, either, but it's worth trying. The tomatoes should still ripen even if the two pieces of the stem don't ever grow back together.
This article walks you through reattaching broken stems: https://www.gardeningknowhow.com/garden-how-to/info/reattaching-broken-stems.htm
And this article describes how to identify whether your tomato plant is one of the types where splinting, splicing and grafting are actually generally successful:
https://www.gardeningknowhow.com/edible/vegetables/tomato/determinate-vs-indeterminate.htm