According to Pleco, 忌口 is treated as a verb (meaning to avoid certain food; to be on a diet). So, why is 你有忌口吗, founded in Memrise, uses 有? Can't it simply be 你忌口吗? or 你忌口什么食物? to ask what kind of food do you avoid?
Why is there 的 in 我吃辣的上瘾?
Why is it 明天可能会下雨 for "It may rain tomorrow," instead of 明天可能下雨?
Hi, I am a native Chinese speaker. For your questions.
忌口 is treated as a verb but also can be used as a noun. But I'd say it's not very common to use 忌口（it's more like fancy Chinese). But if you have to use it, I recommend 你有忌口嗎, because to me it sounds more natural.
Because 辣的 means sth is spicy. You can think of 的 as stuff. For example 甜的（sth sweet), 苦的（sth bitter).
a. 明天可能會下雨 b. 明天可能下雨 are both correct. In a, there is 會 which indicates future in this case.
Hope it helps!
Similar to many Chinese words 忌口 can both verb and noun. in the sentence "你有忌口吗?", it can still be either verb or noun depending on the context.
For examples: When you are ordering food at a restaurant, the waiter may ask you: '先生,你有忌口吗？' (sir, is there anything you don't/can't/won't eat? 忌口 is a noun here, meaning things you'd avoid eating.)
When you are a regular in a fat fighter class struggling to lose a few pounds, you might be asked by other people: '你怎么还是那么重，你有忌口吗？‘ (why are you still this heavy, have you (really) been on a diet? 忌口is a verb here, meaning to be on a diet/to abstain from eating (something)). However using verb this way (有+verb, equivalent to present perfect tense in English) is less common in Northern China but more common in Mandarin spoken by Taiwanese/Cantonese people. Most people would say ‘你忌口了吗？’ using 了 to indicate present perfect tense.
Not answering your question (alisawangr has done that), but Pleco includes a lot of uncommon and/or classical/regional definitions, especially if you've installed all the possible free add-ons. This is great if you're using it to translate from Chinese, but it's better to stick to one of the modern dictionaries (not free) for translating in the other direction. Free Pleco will give example sentences in Classical/highly literary idiom and not tell you.