1) Yes, he can sell the property as a designated authority, but you have to cross check his authority currently is valid or not by checking his position is updated in registrar office of company registered.

2)  An LLP does not have Memorandum and Articles of Association. Instead you can ask them for  Limited Liability Partnership Agreement.

1) An LLP shall have two designated partners and at least one of them shall be resident in India

2) designated partners can sell the property to you after resolution is passed by the partners 

3) if third person is authorised insist that registered POA be executed by LLP authorising person to sell the property 

For purchase of any property from LLP you should acquire the consent of all partners on sale deed or any other collateral document. Any partner who has not given his consent can challenge the sale deed in future.

1. For selling the proeprty of the company, a resolution authorising the representative to sell the company's property to the prospective buyer is to be passed with majority of the partners passing the resolution. 

2. In such cases the seller/representative shall have to produce the copy of the company's resolution before the sub registrar to show that he had been authorised by the company as its representative to sell/alienate the company's properties to the prospective buyer. 

In all the case it is always advisable that you obtain a proper legal opinion before buying the property.

Dear Sir,

1) The incorporation document of LLP may specify who will be the designated partners. Any partner may become a designated partner or cease to be a designated partner in accordance with the LLP Agreement. Thus you should verify the authenticity of the partners position.

2) Every Designated Partner would be required to obtain a “Designated Partner’s Identification Number”(DPIN), verify the DPIN.

3) Designated partners can sell property after consent of all partners is received.

4) If the company has granted third person the authority to sell and register property, you should make sure the third person has a registered and valid power of attorney in his name made by the lap as principal.

Thank you

Your query: Does one of two designated partners (those authorized any execution as mentioned above) can sell the property by registering to me or not?

Ans. No, one of them can’t sell the property because the authorization clearly says that both are authorized ‘jointly’ to execute or authorize the execution of any documents or deeds on behalf of the LLP. So, both of them can jointly sell the property to you and not one of them. So, just be cautious about that.

Your query: If the company decides any third person (other than 5 designated partners) to give authority to sell and register their property by giving company resolution(unregistered), how can I know board resolution is authentic for registration or do I get any issues in future from Company?

Ans. If third person comes into picture, there wouldn't be any board resolution. You have to watch for  Power of Attorney (POA) duly registered and executed by LLP and that POA should specifically state that this third person is duly authorized to sell the property on behalf of the LLP and is authorized to execute the execution of any documents or deeds on behalf of the LLP for the said purpose.

Hope this satisfies your query! All the best!

The Designated Partner are hereby authorized jointly to execute or authorize the execution of any documents or deeds on behalf of the LLP'

it appears that more than one DPs are jointly authorised to execute documents on behalf of the LLP
That means one DP cannot execute any documents on behalf of the LLP
A resolution is not required to be registered. If the LLP appoints a person, other than the partners of LLP, for executing documents on behalf of the company, then the resolution will state so and will be signed by all the partners and the resolution will be on the letterhead of the LLP