grammaticality - Grammar: "I'll try AND help them"

There are tens of questions here on EL&U about the grammaticality of the try and do something construction and its merits compared with the unremarkable try to do something collocation.

However, this question is not related to those in any way. This question is about the grammatical constraints on the use of the try and do something construction.

This morning whilst on a coffee break I realised that the try and do something construction, henceforth referred to as tryand for short, is not a ready replacement for try to do something. So far these are the grammatical constraints that I have noticed:

1. Tryand is restricted to the present tense only:
   
   
   
   
   
   • I try and visit once a week.
   
   
   • *I tried and visited once a week. (ungrammatical with this meaning)
   
   
   • *I tried and visit once a week. (ungrammatical with this meaning)
   
   

I put the two ungrammatical versions there, because it is not clear whether the second verb in the tryand construction is usually present tense or plain form (aka an infinitive).

2. When occurring in the present tense, tryand cannot be used in the third person singular:

   
   
   
   
   
   • I try and visit them.
   
   
   • You (all) try and visit them.
   
   
   • *He tries and visit them. (ungrammatical)
   
   
   • *She tries and visits them. (ungrammatical)
   
   
   • They try and visit them.
   
   



3. Tryand is useable as the complement of other present tense verbs without the third person restriction, or any past time reference restriction:

   
   
   
   
   
   
   • You can try and visit them
   
   
   • He can try and visit them
   
   
   • He would try and visit them
   
   



4. There is also no restriction on either the third person or the use of the past simple if the auxiliary do is used:

   
   
   
   
   
   • She does try and visit every week.
   
   
   
   • She did try and visit them as often as possible though.
   
   



5. This does not work with the perfect auxiliary have where there seems to be a bar on past time reference:

   
   
   
   
   
   • *She has tried and visit them as often as possible (odd or ungrammatical)
   
   
   • *She has tried and visited them as often as possible (ungrammatical with this meaning)
   
   

So, what I have drawn from this is that perhaps tryand cannot be used in any construction where the second verb would have to be inflected.

My questions are the following:

• Are there any further restrictions on the use of tryand which I have missed?




• When the verb try in the tryand construction is present tense, is the second verb also present tense or is it a plain form of the verb (an infinitive)?




• Why exactly does tryand have these restrictions?

Answers to any or all of the questions above would be welcome.