Adding honorific prefix in a compound construction? (E.g. 買ってくれになる)

Question

I'm currently learning how to use くれる/あげる correctly, and I want to practice using 敬語 in my sentence. However, I am not sure where I should put the pre-verb honorific prefix お used in おVERB+になります as I have several verbs combined in my sentence:

お隣りが父にお土産をお買ってくれになりました。

First off, 買う is done on the neighbor's part. Yet, it is "my father" who is receiving the お土産 with the verb くれる. I am uncertain whether I should even use お+連用形+になる in the sentence at all. Perhaps I'm getting the subject all wrong?

Question:

1. How does one turn a compound verb into 敬語?
2. Am I wrong in using 敬語 in this sentence at all?

*Terms such as "compound verb" are used provisionally, since I'm not familiar with linguistics. If wrong, please correct me.

Edit: In another related question asked on HiNative, a native speaker suggested that 贈ってくれる (贈る+くれる) was redundant. Thus, 買ってくれる. Also, apparently が is better than は to mark the subject according to the kind person who offered correction.

Answer 1

Your sentence is unnatural.

おVERB+になります is honorific. The honorific of くれる is くださる。

If you want to use a honorific word in your example, お隣りさんが父にお土産を買ってくださいました would be natural. お隣りさんが父にお土産をお買いになりました and お隣りさんが父にお土産をお買いになってくれました(くださいました) would be probably grammatically correct, but I don't say it like that. I feel they are very polite.

In addition, 二重敬語(redundant keigo) like 先輩がお帰りになられました is generally not allowed. 先輩がお帰りになりました and 先輩が帰られました is already honorific expression. Basically, a word can't be changed to honorific double except some exceptions. On the other hand, 連結敬語 (connection keigo) like お読みになってくださる is generally allowed. They are regarded as each word 読む and くれる is changed to honorific form.

Source: http://www.levelup99.net/businessmanner/cate3post21.html