Oracle 18c

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with src_nodes as (
    select 1 id, 'A' nvalue, date '2021-01-01' vfrom, date '2021-02-10' vto
    from dual
    union all
    select 1, 'B', date '2021-02-15', date '2021-02-28'
    from dual
    union all
    select 2, 'C', date '2021-01-01', date '2021-01-31'
    from dual
    union all
    select 2, 'D', date '2021-02-01', date '2021-02-28'
    from dual
    union all
    select 3, 'E', date '2021-01-01', date '2021-02-28'
    from dual
    union all
    select 4, 'F', date '2021-01-01', date '2021-01-31'
    from dual
    union all
    select 4, 'G', date '2021-02-01', date '2021-02-28'
    from dual
    union all
    select 5, 'H', date '2021-02-01', date '2021-02-28'
    from dual
    union all
    select 6, 'I', date '2021-02-10', date '2021-02-28'
    from dual

),
     src_links as (
         select 1 link_child, 2 link_parent
         from dual
         union all
         select 2, 3
         from dual
         union all
         select 3, 4
         from dual
         union all
         select 5, 6
         from dual
     ),
     -- use "recursive with" method instead of "connect by" to be able to
     -- refine the validity dates as we walk the tree
     hier (id, vfrom, vto, nvalue, lvl, root_id, tpath) as (
         select sn.id, sn.vfrom, sn.vto, sn.nvalue, 1 lvl, sn.id, sn.nvalue || ''
         from src_nodes sn
         where -- start with nodes that have no incoming parent link
             exists(select null from src_links a where a.link_child = sn.id)
           and not exists(select null from src_links a where a.link_parent = sn.id)
         union all
         select sn.id,
                greatest(sn.vfrom, hier.vfrom),
                least(sn.vto, hier.vto),
                sn.nvalue,
                hier.lvl + 1 lvl,
                hier.root_id,
                hier.tpath || '-' || sn.nvalue
         from hier
                  join src_links ln on ln.link_child = hier.id
                  join src_nodes sn on sn.id = ln.link_parent --
             and greatest(sn.vfrom, hier.vfrom) < least(sn.vto, hier.vto)
     ) -- use "depth first" to be able to detect leaf nodes
         search depth first by id set seq,
     hier_leaves as (
         select *
         from (
                  select a.*,
                         -- a difference of one means it's a normal 'depth first' step. otherwise it's a leaf
                         (case lead(a.lvl) over (order by a.seq) - a.lvl
                              when 1 then 'inner'
                              else 'leaf' end) path_type
                  from hier a)
         where path_type = 'leaf')
select hl.tpath, hl.vfrom, hl.vto
from hier_leaves hl;

TPATH	VFROM	VTO
A-C-E-F	01-JAN-21	31-JAN-21
A-D-E-G	01-FEB-21	10-FEB-21
B-D-E-G	15-FEB-21	28-FEB-21
H-I	10-FEB-21	28-FEB-21