Whenever the soil dries out completely it is safe to water your cacti. If you water them to much then they can develop root rot which will kill them.
they are succulents
no yhu need 2 repeat the expermient
For deeper sources, the taproot would be a better choice because it digs deeper into the ground for water and minerals.
To much.
It is phenomena. Answer 2 Phenomena is the plural of phenomenon. But a lot of people don't realise that. In the same way as criterion is the singular pf criteria. You hear people say things like 'the criteria I want for my loudspeakers is clarity'. There's only one 'criteria' here so it should be 'the criterion I want for my loudspeakers is clarity'. I've also heard people refer to cactis. The plural of cactus is cacti. So you don't pluralise it again by saying cactis.
Unlimited supply of fresh water
4 inches
8 glasses but you really should not drink that much also you can consume(drink) more or less if you wish to
you should drink 1 liter of water per day.
Yes, cacti do have seeds. They produce incredibly beautiful flowers which are pollinated just like other plants, by cross pollination or animals.
8 glasses of water
About 9 bottles of water.