Immediate termination without notice or inquiry

I am seeking legal opinions on the following employment dispute. All names and identifying details have been withheld for privacy. A photographer employed at a creative studio in Delhi was terminated with immediate effect after approximately seven months into his second tenure with the same employer. The first tenure had concluded amicably with formal relieving and recommendation letters. He rejoined at the employer's invitation, but the revised appointment letter for the second tenure was never signed by the employee — only by the employer — at any point during the seven-plus months of the engagement. No written warning, show-cause notice, or formal complaint was issued to the employee at any stage of either tenure. The termination was verbal and immediate. The employer's stated basis, communicated only in post-termination correspondence, was "professional misconduct" citing two grounds: (a) content from a private WhatsApp conversation between the employee and a colleague, which the employer came across on a company-owned device, and (b) the employee's modification of a cab invoice — changing the name field to that of a colleague for reimbursement purposes — where the amount was unchanged, no duplicate claim was made, and no financial gain accrued to the employee. Neither ground was ever raised during employment. In a recorded phone call post-termination, the employer explicitly stated that the termination was personal in nature and confirmed that salary payment was contingent on the employee signing the proposed settlement. The Full and Final settlement agreement being demanded contains the following: (i) pro-rata salary for 11 days worked, payable only upon return of assets and signing of the agreement; (ii) a permanent, absolute prohibition on the employee using any work produced during tenure in his portfolio, website, or social media, with a penalty clause equating to full production costs per shoot; (iii) a 12-month non-solicitation clause covering all past and present clients of the employer with no geographic restriction; and (iv) a full waiver of all claims against the employer. The employee has not signed this agreement. Questions for the forum: ---Given that no show-cause notice or domestic inquiry was conducted before termination, and the second appointment letter was never signed by the employee, how strong is the wrongful termination claim under Delhi jurisdiction? Would the employee's conduct of working for seven months be considered implied acceptance of the unsigned letter's terms, including the immediate termination for indiscipline clause? ---Can the employer lawfully withhold earned wages (11 days' salary) as a condition of the employee signing an F&F agreement? Is there any remedy available if the employer refuses to pay without the signature? ---Is the cab invoice modification — where the amount was unchanged, no financial gain accrued to the employee, and no due process was followed — sufficient to constitute gross misconduct warranting summary dismissal? To what extent are the zero-portfolio-usage clause and the 12-month blanket non-solicitation clause enforceable as post-employment restrictions, particularly where the F&F agreement has not been signed? Would the employee's authorship rights offer any protection regarding portfolio use? ---If a former client of the employer independently and voluntarily approaches the employee for work — without any solicitation by the employee — is the employee bound to refuse under a non-solicitation clause, assuming it were otherwise valid? Any views on the above would be greatly appreciated.