Infosys does not provide Offer letter to the individual who has or currently working with its client - is Ericsson a client of Infosys?

i have given Interview recently . After clearing all rounds (technical, managerial and HR) , HR told me that they are going to forward my profile for buisness approval then Background check will take place and then offer letter will released in 10–12 days .
But in application form , i forgot to enter 10th and 12th grades (But i have informed about my academics percentage during HR round which is >70 throughout ).
Also i mistakenly Entered “NO” in “Have you attended XXX interview before” but subsequently informed the HR that i appeared for XXX in 2014 but failed to clear written test. HR just made corrections in the hard copy of my application form with pen .
Yesterday , i got a mail from XXX to sign the New Hire document “New Hire Verification and Affirmation regarding contractual Restriction” and the same i have sent to them fully signed. Also i get to know from one of my friends that XXX does not provide Offer letter to the individual who has or currently working with its client. So i want to know if Ericsson is client of Infosys?
I want to know if i would be getting offer letter from XXX and if yes then in how many days i can expect the offer letter from them (since i have another offer but i want to join XXX at any cost if given opportunity).

Dear friend,
You have written that "Also i get to know from one of my friends that Infosys does not provide Offer letter to the individual who has or currently working with its client ."
I don't understand why a company like Infosys will not issue "Offer Letter". This letter states to a job candidate, where he is expected to report, when he is expected to report, what documents are required from the candidate and above all the salary break up. Without this vital information, how a job candidate can join? If the offer letters are not given then what is the alternative? Possibly company like Infosys may send a mail which is on par with the offer letter.
This is the 21st century and job candidates do not wait at the gate of the companies till someone calls them to come inside!
Therefore, remove worries from your mind as to when you will receive the "Offer Letter". There could be a delay because the environment is always in flux. If their client delays the project, then there will be the corresponding delay to your joining also. But then gentleman, show patience!
Thanks,
Dinesh Divekar

Thank you sir for your reply .
Actually i have a another offer and there joining date is at the end of september and the same has been communicated to Infosys HR during interview . Also the offer which i am having is the client of Infosys so i wont stand a chance to come back to Infosys if there is a delay in my offer letter.

You can join whichever you have got offer of the new company. Once receive offer letter from infosys you may think later. Any how you can convince the employer either infosys or present company to join or relieve. No need to worry join present offer without any prejudices or bias.
Regards,
Anil Kumar KT,
Manager HR & IR.