Gifts (Money & Property) - See Scenario

[Bhups]

Hello,

I would like Tax advice on the following scenario.

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Person A = My mother,
Persons B = 3 siblings
Persons C = Myself and spouse

Person A owns a property in her name (which was previously in joint names with her husband).
Persons C wishes to buy this property while Person A still lives in it and holds a 20% share in it.
Person A wishes to gift 80% of the property to Persons C and hold the 20% share as joint names.
Person A will leave the rest of the share as a Will in the name of Persons C.

The Property has a mortgage, which is being paid by Persons B and C equally.
Person A wants the property to be split equally 5 ways (between Persons A, B and C).
The mortgage will be taken on by Persons C and its amount will be deducted from Persons B and C share of the property.
E.g. Property = £750000
Total Share of Persons B and C = £600,000
Mortgage = £60,000
Total Share of Persons B and C after deducting mortgage = £540,000

Persons C is planning to pay Persons B on a monthly basis (over a period of approx 15 years) around £700 each.

Shared expenses (costs of living) between Persons C per month comes to approx £1,500 (£750 each).

Persons C jointly will have sufficient money from taxed income left over after costs of living is deducted, to pay Persons B each month.
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So, my questions are:

1. Am I correcting in thinking that Persons B will not be liable for inheritance tax on payments made from Persons C?
2a. Can Person A gift a large percentage of the property to Persons C, while still living in it without Persons A or C being liable for IHT?
2b. If Person A cannot gift a large percentage of the property due to still living in it and sharing at least 40% of the property (which includes kitchen, living room, toilet/bathroom and bedroom), then Person A can pay a percentage (I guess 80%) of the full market rent (normally at £87 per week).
2c. If Person A will have to pay a percentage of the rent, then can Persons C gift this money to Person A, just for it to come back as rent to Persons C?.
3. Will Persons C be liable for IHT on the percentage of the property under Person A if she left it as a Gift in her Will to Persons C?

Any other IHT or other tax advise will be great.

Thank you,