Vowel reduction of pretonic [о]

Question

This is a two-part question; I hope that's allowable. I'm aware that an unstressed о is usually reduced, though there are some exceptions -- specifically in borrowed words, such as стерео or радио. All the examples I was able to find, however, had the о in question at the end of the word. I'm interested in how it's treated in a pretonic position (i.e. before a stressed syllable). For example, маоизм: Is that [mɐɐˈizm], [mɐoˈizm] or perhaps even [mɐʊˈizm]? How about Маометто (Italian; stress on the penult)? Is it something that is up to each individual speaker to decide, when to pronounce an unstressed "foreign" о and when to reduce it?

The second part of my question is about whether or not there is a glottal stop in between two reduced vowels that produce identical sounds. For example, сообщить is reduced to [sɐɐpˈɕːitʲ]; is there a glottal stop between the two /ɐ/s, or is it essentially just one /ɐ/ sound held longer than a typical /ɐ/?

Answer 1

1. The prestressed o is also reduced at least in quite a few foreign words or their grammatical derivatives, e.g. баобаб [bɐɐˈbap], теология [tʲɪɐˈɫoɡʲɪɪ̯ə], биотопливо [ˌbʲiɐˈtoplʲɪvə], реостат [rʲɪɐˈstat], даосизм [dɐɐˈsʲizm]. In хаос it's not reduced [ˈxaəs] but in хаотический it is [xɐɐˈtʲit͡ɕɪskʲɪɪ̯].
In маоизм [mɐoˈizm] it's also not reduced and perhaps because маоизм has the cluster of 3 vowels unlike most of the listed nouns.

As far as радио and стерео are concerned, the maintenance of full o appears to be based on another principle, because it's maintained also in адажио, арпеджио, трио, какао, and in Italian names such as Горацио, Базилио, Фабио, Антонио as well.

There's nothing to say about Маометто since it's not a current word in Russian vocabulary, but if the principles just suggested are correct, its 1st o would have to be reduced, but the 2nd would remain intact.

2. Russian doesn't have glottal stops so all vowel clusters are pronounced right on through with full air passage and slight tonal variations or vocal attack between individual phonemes to mark segue.