  Supernova remnants (SNRs) can be rich sources of information on the parent SN
explosion. Thus investigating the transition from the phase of SN to that of
SNR can be crucial to link these two phases of evolution. Here we aim to study
the early development of SNR in more details, paying the major attention to the
transition from the early-expansion stage to the Sedov stage and the role
played by magnetic field in this transition. To this end, spherical
magneto-hydrodynamic simulations of SNRs have been performed to study the
evolution of magnetic field in young SNRs and explore a sequence of the SNR
evolutionary stages in the pre-radiative epoch. Remnants of three supernova
types are considered, namely, SNIa, SNIc and SNIIP, that covers a wide space of
parameters relevant for SNRs. Changes in global characteristics and development
of spatial distributions are analysed. It is shown that the radial component of
magnetic field rapidly drops downstream of the forward shock. Therefore, the
radially-aligned polarization patterns observed in few young SNRs cannot be
reproduced in the one-dimensional MHD simulations. The period SNR takes for the
transition from the earliest ejecta-driven phase to the Sedov phase is long
enough, with its distinctive physical features, headed by the energy conversion
from mostly kinetic one to a fixed ratio between the thermal and kinetic
components. This transition worth to be distinguished as a phase in SNR
evolutionary scheme. The updated sequence of stages in SNR evolution could be
the free expansion (of gas) -- energy-conversion -- Sedov-Taylor --
post-adiabatic -- radiative.
