What's your question? Ask

This cactus is like many others that look like it. It likes to be in the sun, and doesn't mind being dry. You can feed it with a cactus fertilizer every few months. This easy-going cactus is relatively care free. Just water it once every one or two weeks and it will do fine. You can even break pieces off and root it to make another plant!

I am just expressing my own experience; I had this issue last year and at the local HomeDepot they told me to use 1/2 Rubbing Alcohol and 1/2 Water in a spray bottle and then spray all over the plant. I did it once a day for two days and all the spider mites were vanished for good.

Supposedly a little Alcohol does not harm plants.

I have been unable to make an id on the variety of this Euphorbia.
I found this link that may be help to you.
http://www.columbuscactusclub.com/euphorbia-eyassiana.html

You can as long as it remains mild, and there is a little rain in the forecast. This will ensure fast recovery. This is how they will naturally form, but you can keep them trimmed if you would like to shape them.

That is one of many Euphorbia. It will be hard to pin down the species, since there are many, and many of them look pretty close without genetic testing.

most of the Genus contains a toxic sap to some degree, with tree forms being far worse than plants. The thicker the sap, the more irritating it tends to be.

This genus contains trees, shrubs, cacti, succulents, weeds, and flowering plants, and is one of the most broad plant Genus around, so pinning them down is VERY difficult in some cases.

Digging them out before flowering is the best method of control. Broad leaf herbicides can be somewhat effective.

This collection of articles will offer information on many of the plants in the Genus: https://www.gardeningknowhow.com/ornamental/cacti-succulents/euphorbia