What is the angle between the equator of the sun, and the plane of the Earth's orbit I want to know the angle between the plane that passes through the centre of sun and is perpendicular to its spin axis, and the plane that contains the orbit of earth around sun?

Is this a fixed value or it is variable over time (and if so, how does it vary) !
The plane that contains the orbit of the Earth is known as the "ecliptic". The rotation of the sun is tilted by 7.25 degrees to the ecliptic, and this value does not vary over time.

The rotation of the Earth is also tilted, by 23.45 degrees to the ecliptic, it is this angle that causes seasons.

An old paper Position of the Sun's axis describes how the Earth crosses the solar equator on June 4th and Dec. 6th each year.

Nasa has a factsheet, that has this and other information about our nearest star.