Not very much sun would be fine though it would do OK on the north side.
If you want to google it, call it Lamprocapnos spectabilis. The name changers have been around that family.
Very hardy, I don't grow mine in full sun, they're very fleshy and I don't think they'd be happy.
I couldn't get it big enough to count legs Bob
It looks mite shaped though
A possibility not a definite ID
Bombylius major maybe, aka bee fly or bee mimic. Lots about at the moment.
It's grown in flowing water commercially but that might be to avoid it smelling of stagnant water. It does fine in my pond with no flow.
Keep it very wet
I planted some supermarket watercress in my pond years ago, it still appears in greater or lesser amount depending on the season.
Ivy is good ground cover and bulbs grow through.
Are you looking for native plants only Peanuts?
A mower is a very good tool for keeping down the weeds once the bulbs have died back