Hi Sridhar,
Firstly there are quite a few requirements in one single post. From future I would suggest asking in separate post as this would easier for people to search if they are facing a similar issue. Secondly this forum/community is for issues that you have tried to fix yourself but was unable to get the desired result and not for forwarding your requirements without explaining what approach you have taken to resolve it.
Anyhow see response to your requirements: The responses are based on the assumption that you are using Webdynpro (portal) to create/approve expenses report
Requirement 1:
Food Allowance: $750 per day per person within country and $1500 outside country:
If the employee is claiming more than above mentioned amount the min amount should post in 1 GL and excess amount in another GL
E.g: If the employee is claiming $900 GLXXXX1 should post with $750 and GLXXXX2 should post with $150.
You can configure this in table T706B2 for the expense type and select 'Distribution of receipt amount to different wage types' in the Amount Type field - This would work if there is an absolute amount and not for percentage of the receipt amount. This view is used to distribute the receipt amount to two wage types and allow a split posting of a receipt amount to different expense accounts.
Requirement 2:
While posting to Vendor the details of "Tax ID for the Vendor" should also be included... Is this possible?
What do you mean by the vendor? Employee Vendor? - Anyway this looks like a custom requirement. If you have the tax ID stored in SAP then you should be able to interface this to FI with the posting document. look at BAdI Trip_Post_FI
Requirement 3:
Only few expense types should have VAT options to select, is it possible?
I hope you mean the Tax Code field for each receipt line. The field can either be hidden for all expense types or visible for all as standard. If you have set the default VAT codes against each expense types in T706B1 then I am not sure why you want want to do this. If you really have to do this then you would need to maintain values in custom table/set/TVARC table and use this in your logic. Check out badi Trip_web_ckeck
Requirement 4:
Is there any way that employees can directly upload their receipts in the trip and submit it for approval.
Attachments is a standard functionality in SAP T&E. See these post
Transfer of Attachments to Receipts - Travel Expenses - SAP Library
Including Attachments in Web Dynpro Travel Expenses - ERP Human Capital Management - SCN Wiki
Hope this helps.
Ankur