Dear,
As per the best of my knowledge, TUPE transfer means The Transfer of Undertakings (Protection of Employment) Regulations 2006 (SI 2006/246), known colloquially as TUPE, are the United Kingdom's implementation of the European Union Business Transfers Directive. It is an important part of UK labor law, protecting employees whose business is being transferred to another business.
With Secondment, you would normally retain your home country contract of employment and undertake an assignment for a defined period (typically 2-3 years), with the expectation that you would then return to a job in your home country.
Severance pay means the compensation that an employer provides to an employee who has been laid off, whose job has been eliminated, who, through mutual agreement, has decided to leave the company, or who has parted ways with the company for other reasons.
Thanks