I am using my phone, so I apologise in advance that this will not be a thorough treatment of the letter. The absolute conditions for canonical regularisation presented by the Chapter to Rome are (i) the liberty to teach according to the constant Magisterium of the Church and the immutable Truth of apostolic Tradition, including the right to correct and denounce those who publicly profess Modernist errors, liberalism, and the errors of the Council; (ii) the right to use the 1962 missal exclusively and to maintain current sacramental practice (confirmation, orders, marriage); and (iii) the guarantee of at least one bishop.
The hopeful conditions are (i) the right to not seek permission from local bishops to operate; (ii) and the establishment of a Traditional priest as president of the Pontifical Commission, along with the majority of its members. The meanin of the first hopeful condition, which I did not include here, was not clear to me, but it has something to do with the ecclesiastical tribunals being kept in their current state. Somebody please correct me if I am misinterpreting this.
There is more but I am running short on time. Hopefully somebody can be more thorough than me. Au revoir.