Yes, an existing partnership firm can be converted into LLP by complying with the Provisions of clause 58 and Schedule II of the LLP Act. Form 17 needs to be filed along with Form 2 for such conversion and incorporation of LLP.

Yes, any existing private company or existing unlisted public company can be converted into LLP by complying with the Provisions of clause 58 and Schedule III and IV of the LLP Act. Form 18 needs to be filed with the registrar along with Form 2 for such conversion.

No, only private / unlisted public company can be converted into LLP.

Any individual or body corporate may be a partner in an LLP. However, an individual shall not be capable of becoming a partner of an LLP, if—

•  he has been found to be of unsound mind by a Court of competent jurisdiction and the finding is in force
• He is an undischarged insolvent
• He has applied to be adjudicated as an insolvent and his application is pending.

Following are the Government charges to register an LLP :

• Digital signature (DSC) – Rupees 1500-2000 (Depending on the Agency)
• Apply for Director Identification Number (DIN) – Rupees 1000 for two partners
• Get the name of the company approved through ‘Reserve your Unique Name’ service (RUN) – Rupees 200
• Incorporation of LLP– Depends on capital contribution: Contribution up to Rs. 1 lakhs – Rs. 500, Contribution between Rs. 1 and 5 lakhs – Rs. 2000
• File ‘Limited Liability Partnership Agreement– Depends on capital contribution. Contribution up to Rs 1 lakhs
• Rs 50 for filing Form 3 and stamp duty based on the state where LLP is formed
• IEC license: The Government fees for IEC code registration would be Rupees 250 to 300. These are the government costs of registering an LLP, However you will need to pay a few bucks more for professional services which is highly advisable.