It's for clarity. "Ĉivespere" would be a valid construct, but nobody does that.
Are there precise rules for when you can use "ĉi" without "tiu"? Is it just for adverb/ adjective phrases?
Ĉi denotes proximity, with any of the ti correlatives it changes "that" to "this". in such an instance it will usually not have a hyphen. Another major use is as a prefix denoting "this" or "here"; that generally requires a hyphen. But it need not be limited to adverbs, f.e. ĉi-jara, ĉi-flanka and ĉi-fojo are all terms I've seen recently.
Precise rules? "Is the meaning clear? if not, try something else that is."
In Esperanto you don't say "I ate toast in the morning" you say "I ate toast morning-ly" with an adverb. Same with "this-evening-ly"
Obviously it describes the word ŝatas, which is the only verb in the sentence.
I'm not sure but from what I understand about the -ig affix, I think you should say "vi devas komencigi tuj savi la medion!". Could anyone confirm/infirm? I like your sentence, though! :)
Thanks for your like! From what I understand "komencigi" means to initiate an action, to "make begin", thus it would make the "action" the agent of itself, which means the action must be spontaneous, usually a noun or an intransitive verb, here the agent of "komenci" and "savi" is the same one: "vi", and "komenci" is transitive.